SYNTHESIS OF TITANIUM NITRIDE VIA HYBRID NANOCOMPOSITES BASED ON MESOPOROUS TIO2/ACRYLONITRILE
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OPEN Synthesis of titanium nitride
via hybrid nanocomposites based
on mesoporous TiO2/acrylonitrile
Claudiu Locovei1,2, Anita‑Laura Chiriac3, Andreea Miron3, Sorina Iftimie1,
Vlad‑Andrei Antohe1,4, Andrei Sârbu3* & Anca Dumitru1*
In the present study, the synthesis of titanium nitride (TiN) by carbothermal reduction nitridation
(CRN) reaction using nanocomposites made of mesoporous TiO2/acrylonitrile with different content
of inorganic phase were explored. The choice of hybrid nanocomposite as precursor for the synthesis
of TiN was made due to the possibility of having an intimate interface between the organic and
inorganic phases in the mixture that can favours CRN reaction. Subsequently, the hybrid composites
have been subjected to four-step thermal treatments at 290 °C, 550 °C, 1000 °C and 1400 °C under
nitrogen atmosphere. The XRD results after thermal treatment at 1000 °C under nitrogen flow show
the coexistence of two crystalline phases of TiO2, i.e. anatase and rutile, as well as TiN phase, together
with the detection of amorphous carbon that proved the initiation of CRN reaction. Furthermore, the
observations based on XRD patterns of samples thermally treated at 1400 °C in nitrogen atmosphere
were in agreement with SEM analysis, that shows the formation of TiN by CRN reaction via hybrid
nanocomposites mesoporous TiO2/acrylonitrile.
Titanium nitrides (TiN) have been researched extensively due their wide range of interesting properties such
as high hardness, high thermal conductivity, high temperature stability and good corrosion r esistance1–3. In
the recent years, different strategies were used for the synthesis of TiN nanomaterials, such as: (1) nitridation
of Ti-metal or titanium dioxide ( TiO2) with various nitrogen sources (nitrogen or ammonia)2,4,5, (2) reaction
of titanium isopropoxide with anhydrous h ydrazine6, (3) reactive ball milling of titanium powders and urea
at room t emperature7, (4) two-step transition metal halide approach at relatively low temperatures of 400 °C3,
(5) self-propagating high-temperature synthesis of cold-pressed titanium p owder8 as well as (6) carbothermal
reduction of titanium oxide under nitrogen fl ow9–11. One of the mostly reported strategies for the synthesis of
TiN nanostructures is the direct nitridation of Ti/TiO2/TiCl4 precursor in ammonia atmosphere, which is an
environmentally unfriendly method due to the use of dangerous and highly corrosive ammonia as nitrogen
source2,4,3. As a consequence, different ammonia-free methods were developed for the synthesis of TiN such as
hydrazide sol–gel method with subsequent high temperature calcination p rocess6, synthesis of TiN@N-doped
carbon composites from T iCl4 dissolved in ionic liquids like 1-butyl-3-methyl-pyridinium dicyanamide as nitro-
gen/carbon source12, reaction of metallic sodium with ammonium fluotitanate in an autoclave at 650 °C13, as well
as reaction of titanium oxide with sodium amide at 500–600 °C for 12 h in an a utoclave14. However, despite the
relatively low temperatures range used for TiN synthesis, these methods still have some limitations, mostly related
either to the expensive ionic liquids required, or to the extremely poisonous and dangerous reactants used as
nitrogen source1. In this regard, the development of economical and environmentally friendly preparation route
of TiN is highly desirable. As an ammonia free method, carbothermal reduction nitridation (CRN) reaction of
titanium oxide in the presence of carbon and under nitrogen flow has some advantages such as the inexpensive
nature of raw materials and the versatility of the carbon p recursors9–11. Previous researchers have been used
carbon black10,15 and activated carbon9,11 as carbon source for CRN process. As reported, in the synthesis of TiN
by carbothermal reduction nitridation of T iO2, the excess of carbon and a good dispersion of T iO2 in the starting
mixture, along with more intimate contact of the reactants, positively influence the reaction rate and significantly
accelerate the r eaction15. On the other hand, polymer materials that are converted into ceramic materials through
controlled pyrolysis have been successfully investigated due to the possibility to adjust the phase composition,
1
Faculty of Physics, University of Bucharest, 077125 Măgurele, Romania. 2National Institute of Materials
Physics (NIMP), 077125 Măgurele, Romania. 3National Research and Development Institute for Chemistry and
Petrochemistry (INCDCP-ICECHIM), Advanced Polymer Materials and Polymer Recycling, 060021 Bucharest,
Romania. 4Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCLouvain),
1348 Louvain‑la‑Neuve, Belgium. *email: andr.sarbu@gmail.com; anka.dumitru@gmail.com
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Figure 1. FTIR spectra of PAN, 30MZ2 and 50MZ2.
microstructure and morphology of the ceramic m aterials16–19. Based on the above considerations, in the present
study, nanocomposites based on mesoporous TiO2/acrylonitrile were explored for the synthesis of TiN by CRN
reaction. In our case, the polymer material was chosen due to the ability of polyacrylonitrile (PAN) to convert
into carbon materials, when it is thermally treated under controlled atmosphere. PAN was exploited to obtain a
carbon layer on pre-synthesized mesoporous T iO220. The use of hybrid nanocomposites based on mesoporous
TiO2/acrylonitrile could favour CRN reaction due to the high specific surface area that lead to a better interface
between the organic and inorganic phases. Hybrid nanocomposite materials were obtained by radical polym-
erization of a vinyl monomer in pre-synthesized mesoporous T iO2 and further used as starting materials for the
synthesis of TiN by CRN reaction at 1400 °C under nitrogen gas flow.
Results and discussions
Fourier Transform Infrared spectroscopy (FTIR) analysis. Figure 1 show FTIR spectra of synthesized
PAN, 30MZ2 and 50MZ2. As seen in Fig. 1, the main characteristic bands of PAN spectra were assigned as fol-
lows: the band around 3610 cm−1 corresponds to O–H stretching, bands at 2941 cm−1 and 2870 cm−1 are assigned
to symmetric and asymmetric of C–H bond stretching in polymer, respectively, absorption in the range between
2150 cm−1 and 2290 c m−1 are assigned to nitrile (–C≡ N) stretching vibration of the acrylonitrile unit in the
polymer chains, the wide absorbance band around 1580–1620 c m−1 is attributed to –C=C– and –C=N– groups,
1455 cm−1 is a characteristic of the bending vibration of C-H in the C
H2 group, 1352 c m−1 is a characteristic of
the aliphatic CH groups along the PAN backbone, 1241 c m and 1065.27 c m−1 are attributed to the skeleton
−1
vibration of the C–C and C–N groups, r espectively21–24. In the case of hybrid nanocomposites, all the specific
features of PAN are visible. Comparing with PAN, in the FTIR spectra of hybrid nanocomposites a decrease in
the intensity of the characteristic absorption bands can be observed, due to the penetration of the polymer into
the pores of the mesoporous inorganic host23.
Thermal stability study. TGA measurements, performed under nitrogen atmosphere, highlighted the
influence of the mesoporous inorganic host upon the polymer’s thermostability which is highly important for
upper stated applications. Figure 2a presents the TGA plots of hybrid nanocomposites, 3 0MZ2 and 5 0MZ2,
together with TGA curves of PAN and mesoporous T iO2 (indexed as M Z2), in the studied range of temperature.
Based on the TGA results, the stages of thermal treatment chosen in the present work for the conversion of
hybrid nanocomposites to TiN were established.
TGA curves of mesoporous T iO2 (see Fig. 2a) show only a slight weight loss (2.44%) associated with a drying
process-free bounded water loss, indicating the stability of TiO223,25. All other samples presented four degrada-
tion stages, characteristic to the thermal degradation of P AN26–29. The first step in the TGA curve of PAN (see
Figs. 2, 3) is located between 50 °C and 230 °C with a weight change lower than 2%, which should correspond
to the loss of physically absorbed water and/or remaining monomer being present in the polymer. PAN sample
remains relatively stable with a slight weight loss till 230 °C, followed by a faster degradation between 230 °C and
485 °C, which corresponds to the cyclization and pre-carbonization processes26,28. Total weight loss at 700 °C
for this sample reached 54.1%. The most important mass loss ~39% takes place between 230 °C and 485 °C and
involves two stages, as can be seen in the DTA curve from Fig. 2b. For the first stage located between 230 °C and
310 °C, with the maximum temperature T max1 of 267 °C, the weight loss is associated with cyclization of nitrile
groups of PAN molecular chain, representing 14% of the weight loss and it can proceed in either an inert or
oxidizing atmosphere26,27,29. The second stage with a maximum temperature T max2 of 417.16 °C and a weight
loss of 35% is correlated with the formation of an aromatic structure and partial evaporation of HCN and vinyl
acetonitrile29. Finally, within the fourth stage, in the temperatures range of 550 °C and 700 °C, a monotonous
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Figure 2. (a) TGA curves and (b) DTA curves of MZ2, PAN, 30MZ2 and 50MZ2.
Figure 3. TGA and DTA curves of PAN.
Sample Tmax1 (°C) Tmax2 (°C) Weight loss (%)
MZ2 – – 2.4
PAN 268 417 54.1
30MZ2 275 409 32.4
50MZ2 273 410 29.4
Table 1. Data obtained from TGA and DTA curve of MZ2, PAN, 3 0MZ2 and 50MZ2.
decrease of weight loss is observed, corresponding to a mass change of ~6%, which may come from the elimina-
tion of polymer chain fragments26.
The obtained hybrid nanocomposite materials have similar patterns with PAN thermogram showing all the
four steps of thermal degradation presented above. Compared to the polyacrylonitrile used as reference, with a
weight loss of 54.14%, the composites synthesized from PAN and M Z2 show lower decomposition values, due in
part to the thermal stability of the mesoporous inorganic matrix. However, weight loss of polymeric hybrids is far
from the theoretical organic content (50% or 70% AN). This significant difference in mass loss suggests that the
polymer was constricted in the cavities of titanium oxide, supporting the hypothesis that PAN was incorporated
into its pores. Table 1 shows the temperatures for the maxima of the main two stages of decomposition for PAN
and hybrid nanocomposites appearing in Fig. 2b.
Morpho‑structural characterization. Figure 4 shows the XRD characterizations of initial samples M Z2,
PAN, 30MZ2 and 5 0MZ2 (Fig. 4a), hybrid nanocomposites thermally treated at 550 °C (Fig. 4b), respectively.
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Figure 4. XRD patterns of (a) initial PAN, MZ2, 30MZ2 and 50MZ2; (b) hybrid nanocomposites thermally
treated at 550 °C.
Figure 5. XRD patterns of 30MZ2 and 50MZ2 thermal treated at 1000 °C in nitrogen atmosphere; where -
TiO2 rutile, ♦-TiO2 anatase, ◦- TiN crystalline phases.
As shown in Fig. 4a, the XRD pattern of PAN presents two phases, one attributed to the crystalline phase of
PAN and the other one represented by a broad scattering with maximum around 2θ = 25.5° is assigned to the
amorphous molecular chain as reported elsewhere26,30,31. The XRD data (acquired in 2θ range of 15°–80°) of the
mesoporous TiO2 show peaks that correspond only to the crystallographic planes of T iO2 anatase phase (ICDD
00-021−1272). XRD analysis of initial samples (Fig. 4a), 30MZ2 and 5 0MZ2, revealed the structural characteris-
tics of both PAN and TiO2, highlighting the formation of the hybrid nanocomposite. After the thermal treatment
at 550 °C, XRD patterns of hybrid nanocomposite (Fig. 4b) show that peaks attributed to PAN vanished and a
broad peak corresponding to amorphous graphite (G) can be seen around 2θ = 26°, while the diffraction peaks
of TiO2 anatase phase are more defined compared to the initial samples. These observations are in agreement
with literature data20,23 and highlight the pre-carbonization process sustained by the thermal treatment, also seen
in TGA results.
Figure 5 presents the diffraction patterns of 30MZ2 and 5 0MZ2 after the thermal treatment at 1000 °C under
nitrogen atmosphere. XRD patterns of both samples show the presence of T iO2 rutile (ICDD 00-021−1276) and
TiN (ICDD 00-038−1420) phases along with a broad peak attributed to the amorphous with the amorphous
graphite phase with an additionally broad peak located approximately at 2θ = 14 °. Taken in consideration the
initial composition of the hybrid nanocomposites together with the reactions involved during thermally treat-
ments, the broad signal is attributed to trace of amorphous graphite oxide (GO)32. According to these results,
this stage of the thermal treatment leads to the conversion of T iO2 anatase phase into T iO2 rutile phase and to the
initiation of CRN reaction that is highlighted by the presence of TiN phase in the diffraction pattern. The intensity
ratio between the corresponding diffraction planes of the two samples revealed that the CRN process is more
advanced in the sample with lower content of inorganic phase. This fact may come from the lower concentration
of the T iO2 anatase in the hybrid nanocomposite which leads to its more uniform and isotropic distribution,
thus providing a superior dispersion of PAN in the inorganic matrix, as discussed later.
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Figure 6. XRD experimental data with Rietveld refinement of (a) 30MZ2 and (b) 50MZ2 after thermal
treatment at 1400 °C under nitrogen flow.
Sample Def (nm) < ε2 >1/2 a (Å)
30MZ2 154±9 1.2·10-3±0.5·10-4 4.24±1·10-4
50MZ2 196±9 7.2·10-4±0.3·10-4 4.24±0.7·10-4
Table 2. Structural parameters taken from Rietveld refinement of TiN for samples thermal treated at 1400 °C.
The plots of the data acquired in XRD characterization onto both samples after last stage of thermal treat-
ment are presented in Fig. 6, together with Rietveld a nalysis33, respectively residuals, that were performed on
the experimental data to refine the structural parameters. XRD patterns of 3 0MZ2 (Fig. 6a) and 5 0MZ2 (Fig. 6b),
show mainly the crystalline structure of the TiN. However, for both samples some traces of amorphous graphite
and amorphous graphite oxide are also observed as two broad peaks with different intensity ratio, apart from
the diffraction planes of TiN phase. Amorphous graphite phase is more pronounced in 30MZ2 sample due to
the organic/inorganic ratio in hybrid nanocomposite, leading to a higher content of carbon which was not
entirely reduced to carbon monoxide and carbon dioxide in the high-temperatures r egime34. Instead, in 5 0MZ2
sample, the ratio between T iO2 and PAN favored a better reduction rate of the carbon. However, in this case, the
dispersion of PAN in the inorganic matrix is not as good as in 3 0MZ2, as it was observed in the XRD patterns of
samples treated at 1000 °C. Thus, the presence of amorphous graphite oxide phase may come from an oxidation
reaction of graphite at low temperatures during cooling process of the samples. Because cooling routine after
thermal treatments was made passively, temperature drop rate was substantially greater at higher temperatures
than cooling rates for lower temperatures. Taking into account the above considerations, for Rietveld analysis of
30MZ2 sample, an amorphous graphite phase with trace of amorphous graphite oxide was considered, besides
TiN crystalline and amorphous phases. The ratio of G/GO was inverted for the 50MZ2 sample as compared to
30MZ2 sample. Graphite content that remained after the high-temperature thermal treatments was converted
to amorphous graphite oxide at low temperatures in a higher amount for the 5 0MZ2 sample due to the greater
oxygen concentration that came from the T iO2/PAN ratio, together with a poor dispersion of the organic mate-
rial in the inorganic matrix. In order to increase the purity of TiN final product, some parameters such as the
dispersion of hybrid nanocomposites, thermal treatments time and inorganic/organic ratio can be improved.
The structural parameters of TiN obtained from Rietveld refinement performed in MAUD program are shown
in Table 2. The quantitative characterization employed the Rietveld lattice constant (a) and microstructure analy-
sis. The higher value of crystallite size (Def ) and smaller microstrain (< ε2 >1/2) in the 5 0MZ2 sample highlighted
the distribution of mesoporous T iO2 and PAN in the hybrid nanocomposite. Thus, a soldering process between
TiO2 particles occurs in thermal treatment at 1400 °C, which reduces the specific surface area of interaction
with carbon and favouring the appearance of larger crystallites. Due to the small specific surface area of 50MZ2
hybrid nanocomposite in the desorption process of remaining oxygen at lower temperature, fewer structural
defects have been created during the formation of amorphous graphite oxide. In comparison, 30MZ2 sample,
with a finer dispersion presents smaller crystallite size and a bigger value of microstrain due to the higher specific
surface area of interaction in hybrid the nanocomposite.
Figure 7 presents the SEM micrographs of the 30MZ2 (Fig. 7a) and 5 0MZ2 (Fig. 7b) after high-temperature
thermal treatment at 1400 °C. A granular shape of the hybrid nanocomposite can be observed in both samples,
with a good distribution of the particles, as seen better in the lower magnification images. Nevertheless, in
30MZ2 sample (Fig. 7a) the average particles size is noticeably smaller than the one observed in 5 0MZ2 sample
(Fig. 7b), due to the different rates of soldering process between particles during the thermal treatment for each
sample, as previously discussed and as also suggested by smaller crystallite size ( Def ) for the 30MZ2 sample (see
also Table 2).
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Figure 7. SEM micrographs of the sample (a) 30MZ2 and (b) 50MZ2 after last stage of thermal treatment at
1400 °C. The insets represent corresponding higher magnification images, highlighting particles shape and size.
In addition, the particles with rectangular facets noticeable in both samples (especially in the higher magni-
fication insets), may suggest the hybrid nanocomposite took over the cubic crystal structure of TiN, as pointed
out by the XRD spectra, too (see Fig. 6). Not in the least, the predominantly bigger rectangle shape of grains in
50MZ2 sample and mostly with smaller rounded particles in 3 0MZ2 sample sustained as well the values for the
structural parameters given in Table 2 and the corresponding discussion.
In order to confirm the results from morpho-structural characterization, the elemental composition of sam-
ples 30MZ2 and 50MZ2 was measured by EDAX technique. The analysis of the recorded data shows for the sample
30MZ2 an atomic concentration of Ti 41.49 at.%, N 50.11 at.%, C 7.68 at.%, and O 0.72 at.%, respectively, and
in case of the sample 50MZ2 the elemental composition is Ti 55.14 at.%, N 39.48 at.%, C 4.55 at.%, and O 0.83
at.%. Thus, the EDAX measurements further support the TiN formation from hybrid nanocomposite by CRN
reaction, with impurities of carbon and oxygen in different ratio for each sample.
Conclusion
Hybrid nanocomposite based on mesoporous T iO2/acrylonitrile monomers with different content of inorganic
phase, were explored for the synthesis of TiN by CRN reaction. The successful syntheses of PAN and hybrid nano-
coposite were proved FT-IR spectroscopy results. TGA results established the conditions and stages of thermal
treatments used for TiN synthesis. The structural analysis based on XRD analysis of the samples thermal treated
at 1400 °C in nitrogen atmosphere highlighted the formation of crystalline TiN phase as main phase along with
some traces of impurities in the form of amorphous graphite and amorphous graphite oxide. Our results show
that the dispersion of the inorganic phase in the hybrid nanocomposite affects the purity of the final product.
Thus, further work will be focused on the investigation of different synthesis approaches for mesoporous T iO2,
which can improve the dispersion along with the optimization of the parameters of the CRN reaction. Mor-
phological characterization was performed by SEM and the results presented a granular distribution in hybrid
nanocomposites with different size and shape of particles for each sample. SEM micrographs along with elemen-
tal composition from EDAX confirmed the observations made on structural properties obtained from XRD
analysis. According to these results, the proposed method for TiN synthesis, relying on the formation of hybrid
nanocomposites from mesoporous TiO2/acrylonitrile, represents an alternative amiable ammonia-free pathway
of producing TiN-based materials with specific properties that can be tailored to a wide range of applications.
Methods
Materials. All chemicals were purchased from Sigma-Aldrich and they were used as purchased, without
further purification unless specifically mentioned. Mesoporous anatase T iO2 (indexed as M Z2), used in this
study, was received from National Institute for Research and Development in Electrochemistry and Condensed
Matter (INCEMC). The inorganic matrix was obtained by a sol–gel process and Pluronic P−127 as a surfactant.
The received powder has Brunauer–Emmett–Teller (BET) surface area of ~79 m2/g, pore surface area of 90
m2/g , pore diameter in desorption of ~9 nm and pore volume (measured ATP/P0 = 0.99) of ~0.2 cm3 /g , respec-
tively. As a mesoporous material, the average pore diameter of titanium dioxide showed values above the 2 nm
limit. The hybrid composites, 30MZ2 and 50MZ2, (where xMZ2- represents the weight percentage of TiO2 from
inorganic–organic hybrid nanostructures) were obtained by radical polymerization of a vinyl monomer (AN)
in pre-synthesized porous TiO2. Two different content of inorganic phase were used for hybrid nanocomposite
synthesis, 30% and 50% respectively. The polymer composites were prepared by an original approach, consist-
ing of two steps: (1) impregnation/adsorption of the AN in the TiO2 pores assisted by ultrasonication and (2)
polymerization-assisted ultrasonication of the AN. Similar procedures were applied for the polymerization of
AN alone, used as reference.
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Conversion of hybrid nanocomposites to TiN by CRN reaction. In order to obtain TiN ceramic
materials, the hybrid nanocomposites have been subsequently subjected to four consecutive stages of a thermal
treatment under nitrogen gas flow at 290 °C, 550 °C, 1000 °C and 1400 °C, respectively. The first three stages of
the thermal treatment were related to the carbonization of PAN layer deposited in pre-synthesized mesoporous
TiO2, whilst the last one involved the CRN process. It is well-known that the stabilization process is an important
stage of the thermal treatment for producing carbon materials from PAN precursors. As reported elsewhere, the
stabilization process of PAN took place at temperatures between 180 °C and 300 °C35,26. The process is character-
ized by different chemical and physical changes due to the cyclization, dehydrogenation, and oxidation reactions,
where PAN precursors are converted to cyclized ladder structures that are the basic intermediates for the forma-
tion of the turbostratic graphite-like s tructure35,21. If the stabilization process took place in nitrogen atmosphere,
intramolecular cyclization is the dominant reaction35,36. Thermal treatment at temperatures lower than 700 °C
corresponds to the pre-carbonization process, where the chain scissions reaction dominates and the carboniza-
tion of PAN layers take place at temperatures higher than 800 °C26. Based on both, the above considerations and
the results obtained from Thermal Gravimetric Analysis (TGA), our thermal treatment for PAN layer carboniza-
tion includes three stages: 290 °C, 550 °C and 1000 °C. Thus, the hybrid nanocomposites were thermal treated
at 290 °C with 5 °C/min heating rate and 2h holding time, followed by subsequent thermal treatment at 550 °C
with 5 °C/min heating rate and 4h holding time, under nitrogen gas flow. In the following stage, the samples were
thermal treated at 1000 °C with 5 °C/min heating rate with 2h holding time under nitrogen flow. As reported in
the references12,15, a more intimate contact of the reactants significantly accelerates the reaction, especially in its
initial stages. The parameters used in our work for CRN reactions took in account the reported results that show
the kinetics of TiO2 reduction represented as the rate of CO evolution in time during carbothermal reduction
and nitriding of T iO2 reached the maximum value for samples treated at 1395 °C (with 10 °C/min as heating
rate), followed by a rapid decrease to the values close to zero, after 2h, which was assumed to correspond to the
formation of thermodynamically stable c ompounds15. Thus, in the present work we analyzed the possibility to
use a better interface between the organic and inorganic phases given by the hybrid nanocomposites based on
mesoporous TiO2/acrylonitrile as precursors for the CRN reaction, using the isothermal temperature of 1400 °C,
with a heating rate of 10 °C/min and isothermal heating time of 2h. In all stages, the furnace was then cooled
freely at the room temperature under controlled atmosphere.
Characterization. Fourier Transform Infrared (FTIR) spectroscopy analysis of the samples was recorded
on a Nicolet Summit FTIR Spectrometer equipment using 16 scans in the range of 550–4000 c m−1, with a resolu-
tion of 4 cm−1. The samples were analyzed using the ATR accessory, on a ZnSe crystal. The thermogravimetric
analysis (TGA) of the polymer’s inorganic matrix, polymer and hybrid nanocomposites were recorded on TA
Instruments Q500 equipment, as follows: a sample quantity (around 3 mg) was heated in the temperature range
of 20–700 °C, with a speed heating of 10 °C/min. The analysis was performed in a nitrogen atmosphere, the
gas flow in the furnace being 10 ml/min. Differential thermal analysis (DTA) provides detailed information on
the polymer decomposition temperature. The morphology of the samples after CRN process was investigated
by Scanning Electron Microscopy (SEM), using a Tescan Vega XMU-II microscope operating at 30 kV with a
detection chain for secondary electrons. Energy Dispersive X-ray Analysis (EDAX) data were acquired with the
Apreo S LoVac Scanning Electron Microscope using an accelerating voltage of 10kV. Ultimately, the starting
materials and synthesized samples were characterized by X-ray diffraction (XRD) using a Bruker D8 Discover
diffractometer (CuKα= 1.54 (Å) in Bragg–Brentano theta–theta geometry. The scattered X-ray photons from
samples were recorded in the 2θ range of 10°–100° with a scanning rate of 0.04°/s at room temperature (unless
otherwise mentioned). Rietveld analysis was then performed to determine the structural parameters of TiN,
using Materials Analysis Diffraction (MAUD) program version 2.94.
Data availability
All data generated or analyzed during this study are included in the article.
Received: 25 November 2020; Accepted: 28 January 2021
References
1. Shi, H. et al. Synthesis of TiN nanostructures by Mg-assisted nitriding TiO 2 in N 2 for lithium ion storage. Chem. Eng. J. 336, 12–19.
https://doi.org/10.1016/j.cej.2017.11.036 (2018).
2. Canillas, M., Moreno, B., Carballo-Vila, M., Jurado, J. & Chinarro, E. Bulk Ti nitride prepared from rutile TiO 2 for its application
as stimulation electrode in neuroscience. Mater. Sci. Eng. C 96, 295–301. https://doi.org/10.1016/j.msec.2018.11.030 (2019).
3. Choi, D. & Kumta, P. N. Synthesis of nanostructured TiN using a two-step transition metal halide approach. J. Am. Ceram. Soc.
88, 2030–2035. https://doi.org/10.1111/j.1551-2916.2005.00367.x (2005).
4. Chen, Y., Calka, A., Williams, J. S. & Ninham, B. W. Nitriding reactions of TiAl system induced by ball milling in ammonia gas.
Mater. Sci. Eng. A 187, 51–55. https://doi.org/10.1016/0921-5093(94)90330-1 (1994).
5. Kola, P. V., Daniels, S., Cameron, D. & Hashmi, M. S. J. Magnetron sputtering of tin protective coatings for medical applications.
J. Mater. Process. Technol. 56, 422–430. https://doi.org/10.1016/0924-0136(95)01856-5 (1996).
6. Kim, I. S. & Kumta, P. N. Hydrazine sol-gel synthesis of nanostrucutred titanium nitride: precursor chemistry and phase evolution.
J. Mater. Chem. 13, 2028–2035. https://doi.org/10.1039/B301964K (2003).
7. Sun, J. F., Wang, M. Z., Zhao, Y. C., Li, X. P. & Liang, B. Y. Synthesis of titanium nitride powders by reactive ball milling of titanium
and urea. .J. Alloys Compd. 482, 29–31. https://doi.org/10.1016/j.jallcom.2009.04.043 (2009).
8. Carole, D. et al. Investigation of the SHS mechanisms of titanium nitride by in situ time-resolved diffraction and infrared ther-
mography. J. Alloys Compd. 436, 181–186. https://doi.org/10.1016/j.jallcom.2006.07.010 (2007).
9. Ortega, A., Roldan, M. A. & Real, C. Carbothermal synthesis of titanium nitride (TiN): kinetics and mechanism. Int. J. Chem.
Kinet. 37, 566–571. https://doi.org/10.1002/kin.20110 (2005).
Scientific Reports | (2021) 11:5055 | https://doi.org/10.1038/s41598-021-84484-3 7
Vol.:(0123456789)www.nature.com/scientificreports/
10. Lu, Y. et al. Porous TiN ceramics fabricated by carbothermal reduction method. Mater. Sci. Forum 745–746, 667–672 (2013).
11. White, G. V., Mackenzie, K. J. D. & Johnston, J. H. Carbothermal synthesis of titanium nitride. J. Mater. Sci. 27, 4287–4293. https
://doi.org/10.1007/BF00541555 (1992).
12. Fechler, N., Fellinger, T. M. & Antonietti, M. Template-free one-pot synthesis of porous binary and ternary metal nitride@N-doped
carbon composites from ionic liquids. Chem. Mater. 24, 713–719. https://doi.org/10.1021/cm203667g (2012).
13. Wu, M. Low temperature synthesis of nanocrystalline titanium nitride from a single-source precursor of titanium and nitrogen.
J. Alloys Compd. 484, 223–226. https://doi.org/10.1016/j.jallcom.2009.07.061 (2009).
14. Huang, Y. et al. Synthesis of nanocrystalline titanium nitride by reacting titanium dioxide with sodium amide. Mater. Lett. 61,
1056–1059. https://doi.org/10.1016/j.matlet.2006.06.048 (2007).
15. Liko, T., Figusch, V. & Pfichyovfi, J. Carbothermal reduction and nitriding of TiO 2 . J. Eur. Ceram. Soc. 5, 257–265. https://doi.
org/10.1016/S0955-2219(89)80009-3 (1989).
16. Mera, G., Gallei, M., Bernard, S. & Ionescu, E. Ceramic nanocomposites from tailor-made preceramic polymers. Nanomaterials
5, 468–540. https://doi.org/10.3390/nano5020468 (2015).
17. Dumitru, A. et al. Inorganic copolymer based on sylanes and ferrocene monomers, precursors for advanced nanostructured
ceramics. Compos. Sci. Technol. 65, 713–717. https://doi.org/10.1016/j.compscitech.2004.10.004 (2005).
18. Bernardo, E., Fiocco, L., Parcianello, G., Storti, E. & Colombo, P. Review advanced ceramics from preceramic polymers modified
at the nano-scale: a review. Materials 7, 1927–1956. https://doi.org/10.3390/ma7031927 (2014).
19. Dumitru, A., Stamatin, I., Morozan, A., Mirea, C. & Ciupina, V. Si–C–N–Fe nanostructured ceramics from inorganic polymer
precursors obtained by plasma polymerization. Mater. Sci. Eng. C 27, 1331–1337. https://doi.org/10.1016/j.msec.2006.09.004
(2007).
20. Vasei, M., Das, P., Cherfouth, H., Marsan, B. & Claverie, J. P. TiO 2 @c core–shell nanoparticles formed by polymeric nano-
encapsulation. Front. Chem. 2, 1–9. https://doi.org/10.3389/fchem.2014.00047 (2014).
21. Fu, Z., Liu, B., Sun, L. & Zhang, H. Study on the thermal oxidative stabilization reactions and the formed structures in polyacry-
lonitrile during thermal treatment. Polym. Degrad. Stab. 140, 104–113. https://doi.org/10.1016/j.polymdegradstab.2017.04.018
(2017).
22. Ruhland, K. et al. Investigation of the chemical changes during thermal treatment of polyacrylonitrile and 15n-labelled polyacry-
lonitrile by means of in-situ FTIR and 15n NMR spectroscopy. Polym. Degrad. Stab. 146, 298–316. https: //doi.org/10.1016/j.polym
degradstab.2017.10.018 (2017).
23. Nyamukamba, P., Okoh, O., Tichagwa, L. & Greyling, C. Preparation of titanium dioxide nanoparticles immobilized on pol-
yacrylonitrile nanofibres for the photodegradation of methyl orange. Int. J. Photoenergy 1–9(3162976), 2016. https://doi.
org/10.1155/2016/3162976 (2016).
24. Rao, X. et al. Polyacrylonitrile hard carbon as anode of high rate capability for lithium ion batteries. Front. Energy Res. 8, 1–9. https
://doi.org/10.3389/fenrg.2020.00003 (2020).
25. Chen, Y. & Feng, L. Silver nanoparticles doped TiO 2 catalyzed Suzuki-coupling of bromoaryl with phenylboronic acid under
visible light. J. Photochem. Photobiol. B Biol. 205, 1–10. https://doi.org/10.1016/j.jphotobiol.2020.111807 (2020).
26. Lei, S., Cao, W., Fu, Z. & Xu, L. The conjugated plane formed in polyacrylonitrile during thermal stabilization. J. Appl. Polym. Sci.
9, 1–7. https://doi.org/10.1002/app.43890 (2016).
27. Nkabinde, S. C., Moloto, M. J. & Matabola, K. P. Optimized loading of TiO 2 nanoparticles into electrospun polyacrylonitrile and
cellulose acetate polymer fibers. Hindawi J. Nanomater. 1–10(9429421), 2020. https://doi.org/10.1155/2020/9429421 (2020).
28. Karbownik, I., Rac-Rumijowska, O., Fiedot-Toboła, M., Rybicki, T. & Teterycz, H. The preparation and characterization of poly-
acrylonitrile–polyaniline (PAN/PANI) fibers. Materials 12, 1–20. https://doi.org/10.3390/ma12040664 (2019).
29. Monahan, A. R. Thermal degradation of polyacrylonitrile in the temperature range 280–450c. J. Polym. Sci. Part A 4, 2391–2399.
https://doi.org/10.3389/fenrg.2020.00003 (1996).
30. Zhang, H., Quan, L. & Xu, L. Effects of amino-functionalized carbon nanotubes on the crystal structure and thermal properties
of polyacrylonitrile homopolymer microspheres. Polymers 9, 1–12. https://doi.org/10.3390/polym9080332 (2017).
31. Badawy, S. M. & Dessouki, A. M. Cross-linked polyacrylonitrile prepared by radiation-induced polymerization technique. J. Phys.
Chem. B 107, 11273–11279. https://doi.org/10.1021/jp034603j (2003).
32. Jeong, H. K. et al. Thermal stability of graphite oxide. Chem. Phys. Lett. 470, 255–258. https://doi.org/10.1016/j.cplett.2009.01.050
(2009).
33. Lutterotti, L., Bortolotti, M., Ischia, G., Lonardelli, I. & Wenk, H. R. Rietveld texture analysis from diffraction images. Z. Krist. 26,
125–130. https://doi.org/10.1524/9783486992540-020 (2007).
34. Xiaowei, L., Jean-Charles, R. & Suyuan, Y. Effect of temperature on graphite oxidation behavior. Nucl. Eng. Des. 227, 273–280.
https://doi.org/10.1016/j.nucengdes.2003.11.004 (2004).
35. Wu, S., Gao, A., Wang, Y. & Xu, L. Modification of polyacrylonitrile stabilized fibers via post-thermal treatment in nitrogen prior
to carbonization and its effect on the structure of carbon fibers. J. Mater. Sci. 53, 8627–8638. https://doi.org/10.1007/s10853-017-
1894-8 (2018).
36. Gupta, A. & Harrison, I. R. New aspects in the oxidative stabilization of PAN-based carbon fibers. Carbon 34, 1427–1445. https
://doi.org/10.1016/S0008-6223(96)00094-2 (1996).
Acknowledgements
This work was supported by a grant of the Romanian Ministry of Education and Research, CCCDI—UEFISCDI,
thorough projects 40PCCDI−1/2018 and PN-III-P2-2.1-PED-2019-2260 within PNCDI III. The authors thank
to Dr. Carmen Lazau National Institute for Research and Development in Electrochemistry and Condensed
Matter for providing the mesoporous T iO2.
Author contributions
A.D., A.L.R. and A.S. design the experiments and established the methodology. A.S., A.L.R. and A.M. performed
the synthesis of hybrid nanocomposites and data analysis of FTIR and TGA. A.D., C.L. and S.I. performed ther-
mal treatments and XRD analysis. V.A.A. conducted the surface analysis. A.D., A.S. and C.L. wrote the main
manuscript text. All authors reviewed the manuscript. All authors contributed to the discussions, gave their
helpful feedback and approval to the final version of the manuscript.
Funding
Open Access funding provided by University of Bucharest.
Competing interests
The authors declare no competing interests.
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